It's the latest cyber-attack on the Democratic party since WikiLeaks published tens of thousands of hacked emails from inside the DNC and Russian hackers apparently broke into the computers of the Hillary Clinton campaign.
Top Democrats have claimed that Russian intelligence is behind the cyber-attacks as part of an attempt to influence the election.
Documents released appear to include information from U.S. House Democratic Leader Nancy Pelosi's computer.
In a post on his blog, a hacker known as 'Guccifer 2.0' posted an Excel spreadsheet that contains contact information for hundreds of Democrats as well as congressional staff members and campaign personnel.
Investigators concluded that the hacker, who claims to be Romanian, is part of a Romanian intelligence operation.
He also uploaded documents that include account names and passwords for a number of subscription services used by the Democratic Congressional Campaign Committee.